1. Field of the Invention
Tetra calcium phosphate based organophosphorus compositions that have significant cohesive and/or adhesive strength properties and also are physiologically-well tolerated are disclosed herein.
2. Description of the Background of the Invention
Calcium phosphate composites are used as bone substitutes and bone grafts. These calcium phosphate composites tend to form complexes primarily between calcium-based salts through charge interactions. These composites are used as general bone void fillers and generally lack the adhesive strength sufficient to adhere or fix bones together, for example, fractured surfaces. These prior compositions have insufficient chemical interaction between the calcium phosphate composite and the bone surface or other surface materials and lack sufficient strength to be used to attach bone to bone or bone to other materials.
Certain marine species, such as tubeworms and sand castle worms, rely on secreted proteins for adhesion mechanisms (“The tube cement of Phragmatopoma californica: a solid foam,” Russell J. Stewart, James C. Weaver, Daniel E. Morse and J. Herbert Waite, Journal of Experimental Biology 207, 4727-4734, 2004). These adhesive proteins contain a high amount of phosphoserine relative to other amino acids. It should be noted that phosphoserine is also referred to as O-phosphoserine. This is an alternate name for the same material and in the present description we will use phosphoserine. The specific mechanism of the phosphoserine involvement with the proteins is not understood. However, phosphoserine has been reported by Reinstorf et al. to be responsible for a specific interaction with calcium containing hydroxyapatite (HA) of bone in U.S. Patent Application Publication No. 2005-0217538A1. In this publication, the authors describe calcium phosphate cements, which do not contain tetra calcium based compositions, modified with phosphoserine in an amount from 0.5% to 5% weight of the composition. The phosphoserine is described as aiding compressive strength and is used as a surface area modifier in the bone cement material. When phosphoserine is used in the range from 0.5% to 5% weight of the composition, the resulting compositions do not exhibit appreciable bone adhesion properties.